金沙江虎跳峡成因及形成时代探讨

A Discussion on the Formation of the Hutiaoxia Gorge on the Jingsha River

虎跳峡是金沙江峡谷的典型代表,其成因及形成时代涉及金沙江-长江水系发育及其环境效应问题。文中分析研究了虎跳峡附近发育的夷平面、剥蚀面、阶地等区域性的层状地貌,并认为虎跳峡上下游河谷发育历史具有一致性;从地质构造上的分析表明,虎跳峡两侧的玉龙雪山、哈巴雪山为一相对完整的地块,不存在虎跳峡大断裂,因而虎跳峡峡谷是在区域地壳抬升、先成河深切作用下而形成的。根据相关盆地沉积物、玉龙雪山的冰川发育状况、前人在附近发现的哺乳动物化石等,初步认为虎跳峡峡谷形成于中更新世。

The Hutiaoxia Gorge is a typical representative of the gorges on The Jinsha River. The research on its causes and ages of formation has close relation to some vital scientific problems, such as development of the water system of the Jinsha and Yangtze, genesis of the first bend of the Yangtze, evolution of the southeastern Qinghai-Xizang Plateau, formation of the Yunnan-Guizhou Plateau, and so on. In the paper, local stratigraphic landforms near Hutiaoxia Gorge, including planation surface, erosion level and terrace, are analyzed, and it is thought that the development histories of upriver and downriver valleys of the Hutiaoxia Gorge are of uniformity. As for geological structure, the Yulong Snow Mountain and Haba Snow Mountain at the two sides of the Hutiaoxia Gorge are an integrated block, there is no fracture between the two mountains. So Hutiaoxia Gorge should be the result of that an antecedent river cut down the bedrock under the background of tectonic uplift. From the evidences of the correlative sediment in basin, glacial feature, mammalian fossils and the formation of water system of China, it is primarily inferred that the Huitiaoxia Gorge has been formed since Middle-Pleistocene.